In general, a cluster munition means a wide area suppression weapon in which a large bombshell (i.e. a mother bomb) is fired over a target in a state of being packed with several ten to several hundred small sub-munitions (i.e. bomblets) therein, and the bomblets are released or ejected over the target. The cluster munition is called a cluster bomb.
There are various types of bomblets that can be loaded in cluster munitions. A typical form of bomblet is used in dual purpose improved conventional munitions (DPICMs). The DPICMs are manufactured to have a spot ignition structure, such as in a shaped charge, in which each bomblet has a conical penetrator therein.
When the bomblet explodes, the conical penetrator forms a high speed metal form, whereby enough power is generated to penetrate objects several inches thick. After the bomblet explodes, an external bomblet body is fragmented to have a casualty radius of several meters. The aforementioned DPICMs are grenades effective in both purposes of destroying light armored targets and killing personnel but have a relatively high dud rate.
Models, such as M77 and M85 of the DPICM, are extremely widely used in various mother bombs around the world. This means that in order for all models of bomblets to be compatible with one another in terms of the loading and releasing structures and the dropping method thereof, sizes of main parts and appearance features of the bomblets need to be the same or be completely compatible with one another. Therefore, there is a great variety of derivative models of cluster bomblets from past to the present. Even a latest model has a basic ignition structure, a fuse connection structure, and a bomblet body shape very similar to those of other models. In other words, the latest model is limited in a design change.
Meanwhile, there are various methods of dispersing bomblets according to types of mother bombs (artillery-launched, missile-delivered, and air-dropped types). Typically, methods of dispersing include a method of dispersing bomblets in a direction opposite to a flight direction of the bomblets using airflow around the bomblets, a method of dispersing bomblets in a circumferential direction of the bomblets using a spin of the bomblets and inner ejection charges, and a method of forcibly dispersing bomblets in a radius direction of a mother bomb using an explosion of ejection charges in the mother bomb.
As illustrated in FIGS. 1 to 5, an existing cluster bomblet includes a bomblet body 50 and a fuse assembly 60. The bomblet body 50 includes: a cylindrical bomblet body portion 51 packed with high explosives 53 and a support portion 52 having a connecting-tube mounting hole 52a formed in a central portion thereof and connected to an upper end of the cylindrical bomblet body portion 51 to seal the upper end of the cylindrical bomblet body portion 51; a conical penetrator 55 being installed inside a rear end portion of the cylindrical bomblet body portion 51; and a connecting tube 56 being mounted in the connecting-tube mounting hole 52a. The fuse assembly 60 includes an ignition tube igniting the high explosives 53 through the connecting tube 56; a slider 62 installed at a fuse body to be horizontally movable; a starter screw 61 screw-connected to the fuse body to limit the slider 62 to move and rotated by a ribbon 64 unfolded when ejected from a mother bomb, to allow the slider 62 to move; and a stud 65 inserted into a stud insertion hole 52b formed in the support portion 52 and connecting the fuse body to the bomblet body 50, the ignition tube 63 being assembled to the slider 62.
In the bomblet body 50, the cylindrical bomblet body portion 51 and the support portion 52 may be separately formed as illustrated in FIG. 4, but the cylindrical bomblet body portion 51 and the support portion 52 may be integrally formed as illustrated in FIG. 5. The support portion 52 has the connecting-tube mounting hole 52a formed in the central portion thereof, and the stud insertion hole 52b is formed in each of both sides of the connecting-tube mounting hole 52a. The support portion 52 has an assembly surface portion 52′ protruding so as to be placed above the upper end of the bomblet body portion 51 and a side surface portion 52″ extending slopingly downward from an edge of the assembly surface portion 52′ such that a lower portion thereof is assembled to an upper interior of the cylindrical bomblet body portion 51 or is connected to an upper end of the cylindrical bomblet body portion 51.
As illustrated in FIG. 6, the existing cluster bomblets are stacked in a shape in which a bomblet body portion of an upper bomblet is fixed to a support portion 52 of a lower bomblet and a fuse assembly 60 connected to the support portion 52 of the lower bomblet is accommodated in a conical penetrator 55 disposed in the bomblet body portion 51, so as to accommodate more bomblets in a limited space of a mother bomb.
A cluster bomblet is fired over a target in a state of being accommodated in a mother bomb. When the mother bomb arrives over the target, the cluster bomblet is ejected from the mother bomb and is ignited or exploded by an impact caused by the collision thereof with the ground or the target, thereby destroying a light armored vehicle or killing personnel.
While cluster bomblets densely stacked in the mother bomb are rapidly ejected from the mother bomb over the target, a fuse assembly may be impacted by a staked upper bomblet. In addition, while the cluster bomblets are dispersed, the fuse assembly may be impacted by a bomblet body adjacent to a side surface portion thereof. Thus, while the fuse assembly dislodges from the bomblet body or a connection portion is twisted, an inoperation of a fuse can be caused or a misalignment of an explosion system can be generated. As described above, when an impact applied to the fuse assembly acts as a factor in which high explosives of the bomblet are not ignited, the bomblet can not be exploded, thereby generating a non-exploded bomblet.
Of course, most bomblets fall without colliding with one another. However, in a case where the falling bomblets fail to maintain a standing position when colliding with the ground or the fuse assembly, or the fuse assembly of the falling bomblets firstly collides with an inclined ground or a rock, the fuse assembly receives an unintentional great impact. As described above, while the fuse assembly dislodges from the bomblet body or the connection portion is twisted even by the unintentional great impact, an inoperation of a fuse can be caused or an alignment of an explosion system can be twisted. Accordingly, high explosives of the bomblet can not be ignited to generate a non-exploded bomblet.
FIG. 7 illustrates a generation process of a non-exploded bomblet. Part (a) of FIG. 7 illustrates a shape in which bomblets collide with each other when the bomblets are dispersed. Part (b) of FIG. 7 illustrates a shape in which a side surface of a fuse assembly collides with the ground due to an incorrect standing position when the bomblets fall on the ground.
Part (c) of FIG. 7 illustrates a shape in which the fuse assembly dislodges from a bomblet body due to the collision. Part (d) of FIG. 7 illustrates a connection failure of the fuse assembly and a misalignment of an explosion system. Part (e) of FIG. 7 illustrates a damaged shape of the fuse assembly. Parts (a) and (b) illustrate primary causes of generating a non-exploded bomblet. Parts (c) and (d) illustrate specific causes of generating a non-exploded bomblet, caused by the primary causes of Part (a) and (b).
In other words, when cluster bomblets are ejected from a mother bomb, the cluster bomblets are primarily impacted by the mother bomb and an upper bomblet. In addition, while the cluster bomblets are radially dispersed at the same time in a state of being densely accommodated in great numbers, the cluster bomblets are secondarily impacted due to the collision with bomblets adjacent thereto. Finally, the cluster bomblets are thirdly impacted due to the collision with the ground or a rock just before an ignition is operated through an impact function due to the collision with the ground. When the aforementioned impacts are applied to the fuse assembly, components of the fuse assembly may be damaged, the fuse assembly may dislodge from the bomblet body, or an alignment of an ignition tube can be at least in disorder. Finally, high explosives can fail to be ignited, thereby generating a non-exploded bomblet.
The non-exploded bomblet is a factor that may reduce fire power of friendly forces and may cause secondary injuries to civilians. Therefore, various types of self-destruct fuses for removing the non-exploded bomblet have been developed and used.
In this regard, in order to prevent a fuse assembly of a bomblet from dislodging from a bomblet body or a connection portion from being twisted, a technology related to a bomblet having a stud connection structure with increased shearing strength has been developed. In this case, a non-exploded bomblet can be generated as follows.
When bomblets are ejected and dispersed from a mother bomb, a fuse assembly may collide with surrounding bomblets, and components of the fuse assembly may be damaged, so that the fuse assembly may be disabled. In a case where the bomblets free-fall and fail to maintain a standing position when colliding with the ground, or the fuse assembly of the falling bomblets firstly collides broadside with an inclined ground or a rock, the components of the fuse assembly may be damaged, so that the fuse assembly can be disabled.
Therefore, in order to prevent a damage of a fuse assembly and ensure ignition of a bomblet, there is a need for a bomblet having a structure able to secure connection strength between a fuse assembly and a bomblet body and protect a fuse slider at least having a self-destruct function and including an assembled ignition tube.
Meanwhile, as a search result of a prior art for preventing the generation of a non-exploded bomblet, various technologies, such as a technology for igniting high explosives through an auxiliary ignition tube, have been searched for. Some of the various technologies will be introduced as follows.
Korean Patent No. 0306357B1 discloses a self-destruct device for a grenade, in which the grenade free-falling on the ground can be automatically exploded after a certain time has elapsed, workability can be improved by forming an accommodation groove connecting a delay tube assembly packed with ignition powders, delay powders, and connection powders to a slider of the grenade, and the delay tube assembly can block the water penetration through a side surface or an inlet of the slider, thereby preventing a failure incident.
Korean Patent No. 1078153B1 discloses a self-destruct device for a grenade, in which an auxiliary ignition tube can be ignited irrespective of rotational inertia force of the grenade, more grenades can be loaded in a transfer body (shell, rocket, missile, or the like) by reducing a size of a fuse, and the grenade can be ejected at a higher altitude by lengthily forming a delay tube assembly in a U-shape to further increase a self-destruct setting time.
Korean Patent No. 1503786B1 discloses a cluster bomblet having a stud connection structure with increased shearing strength, in which since a head of a stud having a wide cross sectional area receives side shearing load by placing a stepped surface of the stud below a fuse attaching surface, and a leg of the stud does not endure unnecessary shearing load by inserting the leg into a case connection hole in a medium fit manner or a loose fit manner when the leg is inserted into the case connection hole, and then, when the head is inserted into a fuse connection hole, an existing stud connection method can be maintained, a shape specification of a main portion of the cluster bomblet can be compatible with those of an existing bomblet, and shearing load applied to a key connection member (i.e. the stud) can be substantially increased, thereby preventing damage and separation between a fuse and a case fragment even when the cluster bomblet laterally receives a strong impact during the ejection thereof from a cluster bomb and the landing thereof on the ground.